Screw-propeller.



C. E. EVITTS.

SCREW PROPELLER.

APPLICATION FILED MAR. 6. 1915.

1,158,909. Patented Nov. 2, 1915.

CKEv/H's CHARLES E. Ev'i'r'rs, OF POTTSVILLE, PENNSYLVANIA.

ISCREW-PROPELLER.

Specification of Letters Patent.

' Patented Nov. 2, 1915.

Application filed March 6, 1915. Serial No. 12,615.

tain new and useful Improvements in Screw- Propellers, of which thefollowing is a specification, reference being had to the accompanyingdrawings. I

My invention relates to propellers, and

particularly to screw propellers of the ordinary type used forpropelling motor boats or other vessels, whether in air or water.

The primary object of my invention is the provision of a propellerhaving its blades so formed and curved as to obviate slippage andfurther acting to relatively project a column of water directly towardthe rear of the propeller or exert a direct rearward thrust against thewater or other fluid upon which the propeller acts without allowing thewater to pass laterally or radially as it were, of the blades.

A further object of the invention is the provision of a propellerwherein the blades shall not only extend obliquely with relation to theaxis of the propeller, but wherein the outer ends of the blades shall begradually curved rearward, thus preventing slippage and also exerting athrust toward a line formingan extension of the axis of the propeller.

My invention is illustrated in the accompanying drawings, wherein Figure1 is a face view of a propeller constructed in accordance with myinvention; Fig. 2 is a perspective view looking toward the side of thepropeller; Fig. 3 is a diagram showing the manner in which theelliptical curve of the propeller is drafted.

Referring to these drawings, 2 designates the hub of a pro eller and 3the blades thereof. Each bla e at its base extends as usual diagonallyto the axis of the hub. The outer end of each blade is wider than itsbase and each blade. at its outer end edge is disposed at an obtuseangle to the axis of the propeller. Each side edge of the blade is givenan elliptical curve, as shown most clearly in Fig. :2, and therefore theblade itself is curved rearward so that the outer end of the blade is'not only twisted but rearwardly curved, these curves being a section ofan ellipse. The side edges of each blade extend radially to the axis ofthe propeller.

The blade is laid out in the manner shown in Fig. 3 wherein a. is a baseline having a length proportionate to that of the blade and b is a pitchline equal to the pitch of the blade. These lines are divided into anequal number of parts by indices. The lines 0 and d are then drawn fromthe corresponding indices on the pitch line and base line, and the outerintersections of these lines gives the required elliptical curvature forthe blades.

It will be noted from Fig. 2 that the forward and rear outer corners ofeach blade, because of the curvature of the blade, are

disposed rearward of the forward and rear' inner corners of the blade,where the blade joins the hub.

Propellers constructed in accordancewith my invention prevent the water"or other fluid from slipping laterally along the blade of the propeller,and the thrust of the blade is always transmitted directly rearwardtoward a line forming a continuation of the axis of the propeller,thereby securing a CHARLES E. EVITTS. Witnesses D. W. GALL, F. B.WRIGHT.

